Until the success of No Country for Old Men, it was widely assumed that the novels of Cormac McCarthy were unsuitable for feature film. McCarthy’s prose, renowned for its density and precision, was considered too elaborate for adaption — his descriptions too painstakingly rendered, his language often arcane or obsolete — and his themes too esoteric or inscrutable. The bloodshed, too, was a problem: From his Southern gothics to his Western epics, McCarthy depicts violence with surgical care, a style likely to thwart any director whose last name isn’t Peckinpah. When McCarthy’s most accessible novel, All the Pretty Horses, became a listless, disjointed film, it only reinforced the prevailing wisdom that McCarthy was incongruous with Hollywood. Then the Coen brothers, who’ve made a career of defying expectations — who else could adapt Homer into a Depression-era comedy? — found the right tone for the right material with No Country for Old Men. When No Country was awarded Best Picture in 2007, The Road, having already been picked by Oprah and awarded the Pulitzer Prize, became destined for a cinema near you.

The current film is faithful to the book’s events but not its overall spirit. Like the brief novel, the film tells a simple story with harrowing clarity: In the aftermath of a global cataclysmic event, a boy and his father are walking to the sea. Animals are just a memory. Food is nowhere to be found. The boy (Kodi Smit-McPhee) may be one of the last children on earth; so rare is his existence that when a stranger calls him an angel, his father (Viggo Mortensen) responds, “To me, he’s a god.” The boy’s mother, we learn in flashback, committed suicide in the aftermath of the catastrophe, in part due to grief at having given birth at the end of the world. In the battered, ash-covered world they now inhabit, father and son stay alive by “carrying the fire,” which is the father’s way of reminding the boy they’re still the good guys. The bad guys are the cannibalistic death squads patrolling the roads in broad daylight.

The Road is about a man’s heroic attempt to usher his son into a newer, better world. But in the process of enforcing a simple code — “I’ll kill anyone who touches you,” he says to the child — the man’s own goodness is diminished by their encounters with evil, all but eliminating his ability to trust other survivors. Before long, he makes a series of terrible decisions suggesting that morally, he has been undone by his sense of purpose. In a world of bad people, what does it mean to be good? Is a good person who kills a bad one still good?

The film raises old questions anew about the suitability of McCarthy’s fiction for film. The book The Road is arguably unfilmmable, relying on exquisite prose to convey the father’s diminishing authority in what looks like hell on earth. The book was beloved because of the great tenderness passing between the boy and the man. In the film, the tenderness is there, but it’s an enforced tenderness, the moody soundtrack often smothering what might be actual emotion if director John Hillcoat (The Proposition) would introduce a little silence. The richness of the father’s love, so eloquently expressed in the book, is suggested but not fully explored, making The Road a more conventional and therefore less transcendent vision of survival. The film’s production team evokes the apocalypse masterfully, using locations shots in New Orleans, Mount St. Helens and Pittsburgh to create a hazy, low-contrast world of decay. But without the necessary emotional arc, The Road is difficult and unsatisfying at times, a long, gradual grinding down of a father’s strength along with the moral certainty of a man whose final words to his son are “Don’t get too comfortable.”